Spinning apparatus



June 1968 E. G. MONTGOMERY 3,389,429

SPINNING APPARATUS Filed Sept. 15, 1966 INVENTOR EVERETT G.MONTGOMERY ATTORNEY United States Patent 3,389,429 SPINNING APPARATUS Everett Gray Montgomery, Hopewell, Va., assignor to Allied Chemical Corporation, New York, N.Y., a corporation of New York Filed Sept. 13, 1966, Ser. No. 579,151 4 Claims. (Cl. 18-8) ABSTRACT OF THE DISCLOSURE Volatile materials such as monomer and oligomer vapors are removed from the vicinity of a spinneret employed for filament extrusion in an improved manner through the use of a frusto-conical bafile element having the smaller circumference end positioned from to /2 inch from the spinneret whereby the flow of gas employed to remove the volatile materials is conveyed in equal distribution in the immediate vicinity of the filament extrusion and withdrawn through the space between said spinneret and said frusto-conical element adjacent to the spinneret face and downwardly through an intermediate chamber before being discharged into a plenum chamber maintained at a pressure lower than in the spinning chamber to facilitate the removal of said gas and volatile materials without creating a turbulent environment in the area of filament extrusion.

This invention relates to spinning apparatus for manufacture of filaments and fibers.

In the melt spinning of multifilament yarns or tows from polymers such as polycaproamide, it is generally found that the small amounts of volatile materials, for example, e-capro1actam and perhaps oligomers thereof, contained in the polymer vaporize, under the spinning condition. The vapors, during continuous spinning operations, accumulate and condense as liquid near the spinneret. Droplets of condensed liquid which impinge upon the filaments in the spinning operation cause localized weakness and increased frequency of breaks during subsequent drying and winding operations. Condensed liquid which accumulates on the spinneret face may cause malfunction of the spinning operation or necessitate frequent maintenance.

A suggested expedient for solving this problem includes the use of aspiration means for continuously removing volatilized monomer from the region near the spinneret. When spinning nylon yarn from a melt of polycaproamide, al-l process parameters must be maintained within a narrow range. Specifically, large pressure drops of a sudden nature can cause poor yarn or necessitate shut-down to correct the situation. In view of the exacting requirements of a successful melt spinning process, the sacrifice of optimization of any parameter in order to accommodate a process innovation, e.g. an aspiration means, is generally detrimental to product or process results. A satisfactory aspiration means must, therefore, be carefully devised and critically combined with the other elements of the spinning apparatus to co-act with the general functions and requirements of the spinning process.

It is an object of this invention to provide a novel apparatus for the melt spinning of filaments.

It is another object of this invention to provide a melt spinning apparatus having means which insure constant process parameters in the neighborhood immediately below the spinneret orifices Without adversely affecting yarn quality or the spinning process.

These and other objects and advantages of my invention will appear hereinafter from the following complete description of my invention, appended drawings and accompanying claims.

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The objects of this invention are accomplished, in general, by providing a fiber-producing apparatus comprising a spinning chamber; a horizontal multi-orifice spinneret disposed in the top of said spinning chamber, aspiration means disposed around the upper end of said spinning chamber in communication with said chamber via channels piercing the walls therebetween, said aspiration means including a plenum and an exhaust port for discharging a gas from said plenum, and gas inlet means for introducing a gas into said chamber. A pressure drop is imposed between the spinning chamber and the plenum atmosphere to create gas flow from the chamber through the channels, into and through the plenum, and out the exhaust port or ports. Within the spinning chamber beginning a short distance say of an inch to /2 inch beneath the spinneret orifices, there is disposed a baffie element having the shape of a conical section, the lower end of which extends to a point beneath the inlet channels of the plenum. In spinning polycaproamide, utilizing the apparatus of this invention, it is preferred that the temperature of the polymer be in the range of 250 C. to 290 C. and the polymer is extruded in contact with inert cooling gas or vapor in the spinning chamber at a jet velocity usually in the range between 10 and 40 yards per minute. A lower pressure is maintained in the plenum than in the chamber with a variation of pressure of less than 0.5 inch of water throughout the volume of the plenum, the flow rate of gas from the spinning chamber into and through the plenum being maintained between 1 and 20 cubic feet per minute for a chamber about one foot in diameter and being at substantially equal volumetric flow rate at all points along the circumference of the bafile separating the spinning chamber from the plenum.

In a preferred embodiment of practice of this invention, the cooling gas enters the spinning chamber through inlets in the walls thereof having a highest level at 1 below the bottom A of the baflle. In this embodiment, a minor portion, say 20% or less, of the entering gas is drawn upward from the inlet, and a major portion of the entering gas flows downward in the spinning chamber below the inlet, and exits below the inlets. I prefer that the spinning apparatus of my invention have a counter-current cooling gas flow distance, i.e., the distance between the spinneret and the uppermost cool air inlet at least equal to the distance between outermost orifices and preferably between 10 and 20- inches. I have found that extended or increased counter-current cooling gas flow distance assists in avoiding turbulence near the spinneret face and provides a protective vapor film having a high concentration of monomer vapor therealong and a zone of nearly static gas through which the filament passes, thus providing counter-current essentially streamline flow of monomer vapor upwardly toward the gas withdrawal means, thus providing better uniformity in filaments freshly spun, enabling them to be taken up more readily and processed with greater uniformity with attendant achievement of good end product.

The invention will be more readily understood by reference to the accompanying drawing which is a sectional elevation of a spinning apparatus, partly fragmented, of the present invention taken along the vertical axis of the spinning chamber. Referring now to the accompanying drawing, a vertical spinning chamber 1 is defined by cylindrical Wall 2 and a horizontally disposed spinneret 4 having a multiplicity of orifices 6. Aspiration means at the upper end of the spinning chamber includes a plenum 8 surrounding the chamber and provided with exhaust port 10 which is connected to a vacuum or other suitable means (not shown) for withdrawing gas. Inlet channels 14 having inlet point E form a horizontal ring communicating through the inner wall of the plenum 8 with the gaseous atmosphere of the spinning chamber. A bafiie element 16 having a vertically extending lip 18 is positioned beneath the orifices 6 of the spinneret about inch from the bottom of the spinneret plate 4. Bars 20 positioned on the upper ridge of baffie element 16 insure that the bafiie element is maintained at a constant distance over its top from the bottom of the spinneret plate 4. The bafiie element 16 without the lip 18 has a conical configuration and is joined near its bottom to plate 42 disposed beneath the bottom of plenum 8 and inlet channels 14. This baffle extends clear of the inner plenum wall and downward past the inlet channels 14 of the plenum.

Cooling gas inlets 22 in the walls of the spinning chamber are provided for the entrance of cooling gas into the spinning chamber. The top-most of these inlets is positioned in line with point I. Best results are generally obtaned when the top-most cooling gas inlets are at a critical distance below the bottom of the spinneret plate 4, orifices 6 which distance is designated the countercurrent cooling gas flow distance and is at least equal to the maximum distance between outermost orifices 6 and preferably between and inches.

The cooling air or other suitable gas enters a manifold inlet 24, travels around the spinning chamber, travels up a bellows element 26 and then passes through the cooling gas inlets 22 to be in contacting relationship with the freshly spun fibers 28, as shown by dot and dash lines. The bellows 26 is affixed to a support member 29 forming a bottom ear the cylindrical wall 2 of the vertical spinning chamber and having a U shape. The plenum 8 is suspended via a vertical bar 30 within groove 34 containing liquid sealant 32. Groove 34 is positioned in block 36 which constitutes a portion of the cylinder of the vertical spinning chamber 1. The bafiie element 16 is held in place using ears 20 in combination with spring screws 38 which pass through horizontal ring 40 and have heads 43 which bear against annular skirt 42, which is joined to element 16 and forms a part of the baffie. The skirt 42 is immersed in a liquid sealant such as Woods metal.

An outlet (not shown) for the cooling gas which descends in the vertical spinning chamber is provided below the manifold inlet 24.

The plenum should be maintained at a sufficiently elevated temperature to minimize accumulation of condensible material therein.

The baffle element of conical section shape is preferably non-porous and has a rigid construction. It is positioned from the bottom of horizontal spinneret 4 having orifices 6 fixed at a distance of at least & but no more than about /2. It extends beneath inlet channels 14 so that the aspiration means will not adversely affect the freshly spun filaments exiting from the spinneret orifices The inlet channels to the plenum are preferably numerous holes of relatively small size. Usually they are circular, but narrow slits can be used. These channels provide a pressure differential of about 0.05" to about 10 of water between spinning chamber atmosphere and plenum. The plenum is so sized and the channels leading thereto and exhaust port leading therefrom are so sized and spaced as to maintain this pressure differential substantially uniformly within about 0.5" water throughout the plenum volume, and maintained volumetric rate of gas flow which are substantially equal through all successive areas of the wall separating the spinning chamber and the plenum. For this purpose, the plenum cross sectional area suitable will exceed by several fold, the total cross-sectional area of the inlet channels whereby the linear rate of fiow of gas throughout the plenum will be approximately /2 of that through the channels. The channels can then be all of the same size and spaced uniformly and at a single level around the plenum and will then provide a uniform pressure throughout the plenum Sit) volume and equal volumetric rate and flow of gas into all areas around the plenum. The exhaust port or ports will usually be sized with a view to avoid pressure gradients in the plenum; accordingly, they will have relatively large cross-sectional areas. Although, usually the channels are evenly sized and spaced and all at the same level, they can be of different sizes and spacing and at different levels as long as equal volumetric gas flow rates through each suitable area of the plenum are obtained.

In spinning a yarn, utilizing the apparatus of my invention shown in the accompanying drawing, the freshly spun or extruded filaments 28 emanating from orifices 6 undergo solidification starting in the region of the aspiration means under the influence of a counter-current flow of the inert gas or vapor entering through manifold inlet 24, the air flow then passes up within bellows 26 through cooling gas inlets 22 and up within the baffle element 16. The counter-current flow of inert gas constitutes only a minor part or portion of the total fiow of gas entering the chamber through cooling gas inlets 22. Most of the gas entering through cooling gas inlets 22 passes cocurrent with the freshly spun filament and exists through a gas outlet (not shown). The gas passing counter-current the fiow of filament passes up through or within bathe element 16 over bafile element 16 in the say inch headspace above the lip 18 then passes down on the outside of bafiie element 16 toward inlet channels 14. The gas passes then out inlet channels 14 into plenum 8 and is withdrawn through exhaust port 10. This flow of gas carries with it through inlet channels 14 volatized monomer given off by the molten freshly extruded filament in the upper region of the spinning chamber. The filaments further solidify and cool in the lower part of the spinning chamber, below the cooling gas inlets 22.

During the continuous spinning operation, inert gas is drawn into the cooling gas inlets 22 and thence upwardly through the chamber, the rate of gas flow depending upon stack size, yarn type, desired physicals etc., and then through inlet channel 14 after passing around baffle element 16 and lip 18; through the plenum 8 and through the exhaust port 10 to a vacuum pump, Water aspirator or analogous means, not shown, for propelling or transporting gas. The major portion of the entering inert gas, up to say about thereof, descends in the spinning chamber co-current with the filament and is withdrawn at the bottom of the spinning chamber.

The use of monomer bafiie having a conical section and disposed between ,4 and /2 inch beneath the spinneret plate facilitates removal of monomer vapor at the face of the spinneret and reduces air turbulence at the conditioning zone of the stack between the spinneret and the cooling gas flowing upwards. My bafiie element contributes significantly to smooth spinning operations under these conditions whereby uniformly high quality filaments are obtained without interadhesion.

The undesired occurrences of turbulence, cross-flow of gas, and spinneret cooling frequently encountered when aspiration means are applied in spinning to remove volatiles near the point of filament extrusion, are largely avoided utilizing the spinning apparatus of my invention.

In order to provide for periodic inspection and maintenance of the spinneret and associated aspiration means, it is desirable to employ coupling means associated with the chamber wall to facilitate repeated dismantling and assembly of the spinning apparatus. Said coupling means may preferably be located between the aspiration means, although in some embodiments the coupling means may desirably be positioned above the aspirator means. The coupling means shown in the accompanying drawing utilizing a spring screw 38 having screw head 43 bearing against horizontal bafile skirt 42, nuts 39 and horizontal ring 40 has been found to be quite suitable for affixing the bafile element into place. Bars 20 insure a slight head space between the uppermost rim or lip 18 of baffle element 16 and the bottom of the horizontal spinneret 4. Coupling means for the aspiration means must provide an effective air-tight seal so as to prevent extraneous air from entering the spinning chamber. Preferred coupling means should include a deformable, resilient member which can conform the geometrical requirements of the two coupling entities, thereby providing a rapid-acting tight seal which will retain its effectiveness even after many coupling cycles. Specific resilient members include elastomeric O-rings, gaskets and troughs of non-volatile liquids for molten metal e.g., Woods metal into Which one of the coupling members becomes immersed to form an air-tight seal.

The following example describes completely a specific embodiment of my invention illustrative of the best mode contemplated by me of carrying out my invention; but it is not intended to restrict the scope of the invention to the details set forth therein.

Example Employing a spinning apparatus essentially as represented in the accompanying drawing, a polycaproamide polymer having a Formic Acid Relative Viscosity of 45 (as determined by ASTM procedure D-789-53T) and volatiles content of about 1%-3% by weight, was extruded at a temperature of 262 C. and at a jet velocity of about 20-35 feet per minute through a stainless steel spinneret containing 136 round orifices each of 0.018 inch diameter, radially arranged. The spinning chamber into which the filaments were extruded was about 22 feet long and 9 inches in diameter. It was supplied with 41 cubic feet per minute of air at 82 F. entering via manifold inlet 24, up through bellows 26 and through cooling gas inlets 22 to equalize pressures, starting at level I about 12 inches below the spinneret. The plenum 8, as shown in the accompanying drawing, was pierced by circular channels each about inch in diameter and A inch long, uniformly set in a ring having a diameter of about one foot.

A pressure differential as against the atmosphere of the spinning chamber of 0.6 inch of water was maintained throughout the volume of plenum 8 by means of a vacuum pump acting through a condenser for recovery of monomer and communicating with the plenum through exhaust port 10. The volumetric flow rate through the plenum to the exhaust pump was not more than 8 cubic feet per minute, less than /5 of the total air, the remainder of the air exiting at the bottom of the chamber where the filament emerged.

During continued spinning, little condensed monomer was observed to form on equipment surfaces in the region of the spinneret. The yarn bundle remained unaffected by the action of the aspirator means, and the surfaces of the spinneret retained constant desired temperature.

Although certain preferred embodiments of the invention have been disclosed for purpose of illustration, it will be evident that various changes and modifications may be made therein without departing from the scope and spirit of the invention.

I claim:

1. A filament producing apparatus comprising a vertical spinning chamber, a horizontal multiorificc spinnerct forming the top of said spinning chamber, means including a plenum around the upper end of said spinning chamber and in communication with said spinning chamber via inlet channels piercing the wall therebetween for withdrawing gas from said spinning chamber, a frusto-conical bafile element surrounding the area of travel of filaments from said spinneret and having its smaller circumference substantially above said channels and spaced to /2 inch from the said spinneret and in proximity to the outermost orifices and its larger circumference disposed below said inlet channel to said plenum, and a cooling gas inlet to said chamber disposed below said larger circumference so as to avoid inlet turbulence in the vicinity of the spinneret face.

2. A filament-producing apparatus according to claim 1 wherein said cooling gas inlet is disposed at a distance below said spinneret between 10 and 20 inches.

3. A filament-producing apparatus according to claim 2 wherein said inlet channels piercing the wall of the plenum are in the form of small holes sized to maintain pressure differential in the range between about 0.05 and 10" water between the spinning chamber atmosphere and the plenum when gas is being exhausted from the plenum, and wherein said holes are spaced to maintain volumetric rate of gas flow which is substantially equal :at all points along the circumference of the baffle.

4. A filament-producing apparatus according to claim 1 wherein the smaller circumference of the frusto-conical baffle element is a vertically extending lip spaced about inch from the horizontal multi-orifice spinneret forming the top of the spinning chamber to provide an outlet from the spinning chamber adjacent to said spinneret.

References Cited UNITED STATES PATENTS 1,814,468 7/1931 Dreyfus et al. 2,763,891 9/ 1956 Moos et a1. 3,257,487 6/ 1966 Dulin. 3,271,818 9/1966 Bryan. 3,313,001 4/1967 Finzel et al.

WILLIAM J. STEPHENSON, Primary Examiner. 

